Well, with more children the better a sling becomes, I'm really loving back carrying in a Kozy or Patapum. But other things have also come in quite handy... I can't keep my floors spotless and he gets into a lot of little pieces of hair, trash, food crumbs, stuff tracked in from outside. He can not have gluten, yet my 3yr old can into the living room w a cookie 2 days ago. Now he can't be on the floor until I scrub it. He loves to crawl around, play on his tummy, sit and play, etc and to keep him safe from the other things in the house I can't get to everyday, I will use a play pen.
: (we're not talking all day here, 35 mintues while I cook dinner, 3 min while I get the olders out to the bus, etc)
Even in AP there can be a place for a Johnny Jumper, a swing, an exersaucer, a play pen, the key is that these things are not a replacement for mama time and interaction or a "babysitter", they are tools to allow children to explore their world safely when it might not always be so safe.
BTW - I use the Johnny Jumper while I clean the kitchen or cook, he can see me and we can talk.
I'm not as young as I used to be and all day babywearing wears me out!!! I'm so old...